As an object identifying apparatus, for example, an apparatus used for a driver assistance system such as an ACC (Adaptive Cruise Control) or the like is well-known to reduce an operating load of a driver of a vehicle. In a vehicle drive supporting system, it is required to properly distinguish and identify an object such as an obstacle, a leading vehicle, a traffic lane, or the like, in order to achieve various functions such as an automatic braking function or an alarm function to prevent a vehicle from crashing into an obstacle or the like and to reduce a shock at a crash, a vehicle speed adjustment function for maintaining a distance between itself and the leading vehicle, and a function for supporting prevention of a departure from a driving lane. Accordingly, various object identifying apparatuses have been conventionally presented.
Japanese Laid-open Patent Application No. 11-175702 discloses an object identifying apparatus for identifying a traffic lane (object), in order to detect a line in a road image (photographic image) acquired by capturing an image and to detect a relative displacement of a vehicle with respect to a traffic lane line (white line) for dividing driving lanes of vehicles. This object identifying apparatus is used to overcome problems in that sunlight or the like causes a specular reflection when there is a puddle on the road due to rain. Thus, the puddle is imaged with brightness of a similar degree as the traffic lane line (white line) on the road, and a portion of the puddle is misrecognized with the traffic lane line.
In detail, in order to remove the portion of the puddle from the image of the road prior to a white line identification process, the portion of the puddle is removed by eliminating a specular reflection component alone from the image of the road, and the white line is recognized from residual scattered light component. A method for eliminating the specular reflection component alone uses facts in that a horizontal polarized component of the specular reflection is approximately zero at Brewster's angle and the scattered light component includes a vertical polarized component and a horizontal polarized component approximately at the same amount, and conducts the following. That is, the method calculates a difference between the vertical polarized component and the horizontal polarized component in the image of the road, and multiplies a difference value with a correction coefficient for eliminating the specular reflection component in response to an incident angle included in the horizontal polarized component, so as to calculate the specular reflection component. Next, the method subtracts the calculated specular reflection component from the horizontal polarized component, and acquires an image of a scattered light component from which the specular reflection component alone is eliminated from the image of the road.
However, regarding the above-described conventional object identifying apparatus for identifying an object existing in an image pickup area, there are insufficient types of objects possible for the apparatus to conclusively specify what an object is. The conventional object identifying apparatus is confined to types of behaviors of objects used to identify an object. That is, if the types of behaviors of objects used to identify an object are increased, a segmentation of object identification can be further segmented. As a result, an accuracy of object identification can be improved, and the types of behaviors of objects can be increased.
For example, one of the conventional object identifying apparatuses identifies a difference between amounts of reflected light (amounts of light received) from objects existing in an image pickup area, that is, the white line (object) on a road due to a luminance difference in a photographic image. In this object identifying apparatus, the white line on the road is identified from other objects by using a feature of reflected light being different. In a case of identifying an object by using this feature, as described in Japanese Laid-open Patent Application No. 11-175702, an object (puddle or the like) having an amount of reflected light being approximately the same as that of the white line cannot be distinguishably identified from the white line. In response to this problem, like the object identifying apparatus disclosed in Japanese Laid-open Patent Application No. 11-175702, it is possible to distinguishably identify the white line and the puddle which are objects having approximately the same amount of the reflected light, by using the specular reflection.
In addition, for example, in other conventional object identifying apparatuses, a shape of an object as another feature in the photographic image is used, and the shape of the object comprehended from the photographic image is compared with a shape template of an object to be conclusively specified to identify the object.
Since types of features of an object used to identify an object are limited, the above-described problems, regarding insufficient types of objects possible for the apparatus to conclusively specify what an object is, are raised not only to the object identifying apparatus used for the driver assistance system but also to various object identifying apparatuses including an apparatus used for a robot control.
Since an expense is increased, it is not preferable to additionally prepare a new detection device for detecting a new feature in response to increasing types of behavior of objects used to identify an object, to overcome the above problems. Accordingly, it is beneficial in a viewpoint of expense, if it is possible to detect the new feature by using an imaging part which is a detection device generally used to detect a reflection light amount (luminance) from an object, in the conventional object identifying apparatus.
Also, as another conventional object identifying apparatus, Japanese Laid-open Patent Application No. 2009-59260 discloses a three-dimensional object identifying apparatus in which even if two objects, which are the same color and are overlapped with each other, can be appropriately distinguished. The three-dimensional object identifying apparatus uses a feature in that main axis directions of polarized lights of two objects being the same color are not identical, and distinguishably recognizes two same color objects even if these objects are overlapped. In detail, the three-dimensional object identifying apparatus acquires an image through multiple polarizers, calculates a polarized component in a predetermined image portion acquired respectively from the multiple polarized lights being different polarization directions, by using a photo acceptance amount of the predetermined image portion, and also, calculates the polarized component for the entire image. Next, the three-dimensional object identifying apparatus segments an area in which the main axis directions of the polarized lights included in the polarized component are identical, calculates a movement direction of each of the segmented, areas, and identifies an image portion including areas in which the movement directions are the same, as a single object.
In the above conventional three-dimensional object identifying apparatus, in general, by using luminance differences in the photographic image, an edge is extracted between a plane object (for example, asphalt of a road surface) existing in a predetermined plane and a solid object (for example, a leading vehicle) having an outer surface facing towards a different direction than a direction of the predetermined plane. Thus, an area segmented by the edge is recognized as the solid object. However, in a conventional method using luminance differences to distinguishably identify the solid object and the plane object, there are problems in that if the luminance differences are not distinctly shown in the photographic image, it is difficult to identify separately the solid object and the plane object at a high accuracy.
Also, the above conventional three-dimensional object identifying apparatus, in general, by using luminance differences in the photographic image, an edge is extracted between a plane object (for example, asphalt of a road surface) existing in a predetermined plane and a solid object (for example, a sidewall at a road edge, a guard rail, a power pole, a street lamp, and obstacles at the road edge such as a step of pedestrian path and the like) having an outer surface facing towards a different direction than a direction of the predetermined plane. Thus, an area segmented by the edge is recognized as the solid object. However, in a conventional method using luminance differences to distinguishably identify the solid object and the plane object, if there is a portion having greatly different luminance in the same plane object, a border of the portion is inappropriately extracted as an edge. There is a problem in that even the single plane object includes the portion, the portion and another portion in the same plane object are improperly recognized as separate objects. In detail, for example, a great luminance difference is shown between a sunlit portion and a shaded portion on a road surface. As a result, the shade portion (a weak luminance portion) is improperly recognized separately from the sunlit portion (a strong luminance portion). Due to this improper-recognition, for example, if the ACC is applied, the ACC may recognize the shade portion as an obstacle such as the sidewall existing at the road edge, and may conduct a collision avoidance operation. Thus, this improper recognition may cause a wrong control or a wrong process.
The above problems are raised not only to the three-dimensional object identifying apparatus used for the driver assistance system but also to various three-dimensional object identifying apparatuses including an apparatus used for the robot control.
Since an expense is increased, it is not preferable to additionally prepare a new detection device for detecting a new feature in response to increasing types of behavior of objects used to identify an object, to overcome the above problems. Accordingly, it is beneficial in a viewpoint of expense, if it is possible to detect the new feature by using an imaging part which is a detection device generally used to detect a reflection light amount (luminance) from an object, in the conventional three-dimensional object identifying apparatus.